Method and apparatus for magnetic currency detectors



April V12, 1966 T. H. SMITH ETAL.

METHOD AND APPARATUS FOR MAGNETIC CURRENCY DETECTORS 12 Sheets-Sheet 1Original Filed Oct. 27, 1959 INVENTORS THEooo/ef ff SM/rf/ /a-Ma/voAwa/WF@ n .w wam April 12, 1966 T. H. SMITH ETAL 3,245,534

METHOD AND APPARATUS FOR MAGNETIC CURRENCY DETECTORS Original Filed Oct.27, 1959 12 Sheets-Sheet 2 April l2, 1966 T. H. SMITH ETAL METHOD ANDAPPARATUS FOR MAGNETIC CURRENCY DETEGTORS l2 Sheets-Sheet 3 OriginalFiled Oct. 2'?, 1959 Ho 75k X l mu. WEMM IWW. mi f5@ T. H. SMITH ETALMETHOD AND APPARATUS FOR MAGNETIC CURRENCY DETECTORS April 12, 1966Original Filed Oct. 27, 1959 N\%1V M NS. .IF lu M MM M H Q\v\( m O H wwwM M o M V I W w N Sv vim/.V .mbv m ,w m *M O o a www. n n v/ E @mmf n@fl 6W smv Qw Qml Y uom, mmv .w wam' wmww www .W I mmv 1| f www vm mmvNRV i i 39|) New 1 j A l 4\ www m; A W/ aow 1\ ONM/z umm wm m www wwwWVM, $1 www N. mg www: 5T mmmV Qmrxwlxll April 412, 1966 T. H. SMITHETAL METHOD AND APPARATUS FOR MAGNETIC CURRENCY DETECTORS l2Sheets-Sheet 5 Original Filed Oct. 27, 1959 mw Mm H ,d MM. NQ- I M a QSw m o M a W Nnl Y Svwv 5 Nvhv Q\\a/\ April 12, 1966 T. H. SMITH ETALMETHOD AND APPARATUS FOR MAGNETIC CURRENCY DETECTORS l2 Sheets-Sheet 6Original F'iled Oct. 27, 1959 mbv Ik? m Q5 .M M m www., E H @bv .t wwwm5. i M v/v o l w w www mm? QBW 00A/440 MBH/YK@ April 12, 1966 T. I-I.SMITH ETAL 3,245,534

METHOD AND APPARATUS FOR MAGNETIC CURRENCY DETECTORS Original Filed Oct.27, 1959 l2 Sheets-Sheet '7 April 12, 1966 T. H. SMITH ETAL 3,245,534

METHOD AND APPARATUS FOR MAGNETIC CURRENCY DETECTORS Original Filed Oct.27. 1959 l2 Sheets-Sheet 8 April 12, 1966 T. H. sMrrH l-:TAL

METHOD AND APPARATUS FOR MAGNETIC CURRENCY DETEcToRs original Filed oct.27, 1959 12 Sheets-Sheet 9 F1 -EQ y/:r2.1: I

INVENTORJ fffao @e5 H. SM/rv J/GMu/Yo Kew/w @C 4r rx Oom/wo A4. D4/wvoApril 12, 1966 T. H. SMITH ETAL METHOD AND APPARATUS FOR MAGNETICCURRENCY DETECTORS 12 Sheets-Sheet 10 Original Filed Oct. 27, 1959 B MWanx Q oww April l2, 1966 v T. H. SMITH ETAL METHOD AND APPARATUS FORMAGNETIC CURRENCY DETECTORS l2 Sheets-Sheet l1 Original Filed Oct. 27,1959 IN VEN TORS April 12,

T. H. SMITH ETAL METHOD AND APPARATUS FOR MAGNETIC URRENCY DETECTORSOriginal Filed Oct. 27. 1959 12 Sheets-Sheet 12 /saqrl INVENTRJ725000,66 H 5/7/71/ 5/6Mu/v0 Kef/V52 .D0/mwa M D/wra United StatesPatent 3,245,534 METHOD AND APPARATUS FOR MAGNETIC CURRENCY DETECTORSTheodore H. Smith, Dunedin, and Sigmund Kramer, Orlando, Fla., andDonald M. Danko, Cleveland, hio, assignors to National Rejectors, Inc.,St. Louis, Mo., a corporation of Missouri Continuation of applicationSer. No. 849,066, Oct. 27, 1959. This application st. 14, 1963, Ser. No.317,103 Claims. (Cl. 209-4113) This invention, which is a continuationof application Serial No. 849,066, tiled Oct. 27, 1959, now abandoned,relates to improvements in currency detectors. More particularly, thisinvention relates to improvements in methods and apparatus foridentifying authentic paper currency.

It is, therefore, an object of the present invention to provide animproved method and apparatus for identifying authentic paper currency.

For a number of years, the merchandise vending machine industry has feltthe need of methods and apparatus for identifying authentic papercurrency and for separating that currency from spurious paper currency.Until such methods and apparatus become commercially avail able, theprice ranges of the articles that can be vended by merchandise vendingmachines will necessarily be somewhat limited. In recognization of thislong-standing need, a number of devices have been proposed; and some ofthose devices have been built. However, none of those devices, foridentifying authentic paper currency and for separating that currencyfrom spurious paper currency, has proven to be commercially acceptable.Some of those devices were unduly large and bulky, others were undulycomplex and costly, and still others failed to provide sutticientlyprecise and accurate identitication of the authentic paper currency. Forthese various reasons, prior devices for the identication of authenticpaper currency and for the separation of that currency from spuriouspaper currency have been found to be objectionable. The presentinvention obviates these objections by providing apparatus that canidentify authentic paper currency and separate that currency fromspurious paper currency, and that is compact and simple and thatprecisely and eiectively identities authentic paper currency.

Most of the prior devices for the identification of authentic papercurrency and for the separation of that currency from spurious papercurrency utilized optical methods. Specitically, most of those devicesilluminated an inserted bill and then compared predetermined portions ofthat bill with a standard. The optical methods utilized by those deviceskept those devices from being as eiective in testing worn paper currencyas they were in testing fresh paper currency, because worn papercurrency usually is dirty and has less contrast than does fresh papercurrency. Moreover, worn paper currency is usually wrinkled, and thepresence of wrinkles can adversely affect the operation of devicesutilizing optical methods. In addition, the optical methods can beadversely affected by aging of the lamps used to illuminate the insertedbills; and those methods can be adversely affected by the memorycharacteristics of the photoelectric cells employed in carrying outthose methods. Furthermore, the optical methods may become even lessefcient where the atmosphere tends to become dirty, smoky, or foggy. Forthese various reasons, devices that utilize optical methods foridentifying authentic paper currency and for separating that currencyfrom spurious paper currency are objectionable. The present inventionobviates these objections by utilizing a magnetic method of identifyingauthentic paper currency and for separating that currency from spuriouspaper currency. Such a method permits precise and accurateidentification of authentic paper currency irrespective of thecleanliness or lack of cleanliness of that currency and irrespective ofthe absence or presence of wrinkles. Moreover, that method is notsubject to the problems inherent in the aging of lamps or in the memorycharacteristics of photoelectric cells. Also, dirty, smoky or foggyatmospheres will not reduce the efficiency of that method. It is,therefore, an object of the present invention to provide a magneticmethod of identifying authentic paper currency and of separating thatcurrency from spurious paper currency.

Traditionally, certain portions of the paper currency of the UnitedStates of America are printed with ink that has magnetic properties. Thepresent invention utilizes the magnetic properties of the ink on thoseportions of the paper currency to generate signals and then uses thosesignals to cause the paper lcurrency to be accepted. The

present invention does this by causing relative movement between thoseportions of the paper currency and a magnetic head; that relativemovement causing the ink on those portions of the paper currency to varythe magnetic reluctance of that magnetic head. That variance, in themagnetic reluctance of 'that magnetic head, causes the coil or coils onthat head to experience minute voltage variations. Those minute voltagevariations areamplilied and used to cause the paper currency to beaccepted. It is, therefore, an object of ythe present invention toprovide relative movement between a biil and a magnetic head to vary themagnetic reluctance of that head and thereby cause the coil or coils onthat head to experience voltage variations.

Each diiferent denomination of paper currency of the United States ofAmerica has a distinctive portrait thereon, and each of those portraitsis set od against a background of darke-r tone. Those backgrounds areactually grids formed from tine, black, vertical and horizontal lines;and those lines are usually formed from ink having magnetic properties.The vertical and horizontal lines of those grids are spaced apartpredetermined distances; and, therefore, when relative movement betweena bill and a magnetic head is etfected at a predetermined rate, in adirection perpendicular to the vertical lines or to the horizontalVlines, the voltage of the coil or coils of the magnetic head will varyat a predetermined rate. The grid lines have predetermined Widths; andthose widths coact with the relative movement at the predetermined rateto predetermine the durations of the voltage variations. The voltagevariations thus vary at a predetermined rate, and they havepredetermined durations; and those voltage variations will be introducedinto a tuned amplifier which can respond to those voltage variations tocause the bill to be accepted. Such an arrangement is very desirablebecause it provides a direct and immediate testing of a -billandobviates all need of a negative, of a record, or some other simulationof portions of a standard bill. Further, such an arrangement obviatesall of the problems, costs, and uncertainties inherent in trying toalign and register an inserted bill with a negative, a record or someother simulation of portions of a standard bill. It is, therefore, anobject of the present invention to provide relative movement between thegrid lines in the portrait background of a bill and a magnetic head toobtain voltage variations in the coil or coils of said head and to usethose voltage variations to cause that bill to be accepted.

The magnetic properties of the ink used inrengraving,

low signal-to-noise ratios. This means that thermionic emission,transients and other noise can produce voltage variations that cansimulate the voltage variations generated by relative movement betweenthe grid lines, in the portrait background of a bill, and the air gap ofa magnetic head. Because the magnetic properties of the ink used inengraving the portrait backgrounds of currency of the United States ofAmerica are wholly and completely beyond the control of manufacturers ofcurrency detectors, there are positive limits to the signal-tonoiseratios of the voltage variations generated by the grid lines in theportrait backgrounds of bills. As a result, the problem ofdiscriminating between voltage variations due to the grid lines andvoltage variations due to noise is critical. For example, it would beimpractical to base the acceptance or rejection of an inserted bill onthe mere counting of a predetermined number of voltage variations as theportrait background of that bill moved past the air gap of the magnetichead, because a sizable and unpredictable proportion of those voltagevariations could be due to noise rather than to grid lines. Further, itwould not be satisfactory to base the acceptance or rejection of aninserted bill on the repetition rates of the leading and trailing edgesof the grid lines because voltage variations due to noise couldoccasionally have those repetition rates. To be truly satisfactory, theacceptance or rejection of an inserted bill should be based upon thephase and the duration, as well as the repetition rate, of the voltagevariations experienced as the portrait background of a bill is movedpast the air gap of a magnetic head. The present invention bases theacceptance or rejection of an inserted bill upon the phase and durationand the repetition rate of the voltage variations ex perienced as theportrait background of a bill is moved past the air gap of a magnetichead; and, in doing so, that invention provides reliable identificationof authentic currency and reliable rejection of spurious currency.

The present'invention provides bill transports that hold the insertedbill immediately adjacent the magnetic head throughout the time theportrait and the background for the portrait (and the background for theportrait) are in register with that head. The portion of the back.-ground between the leading edge of the portrait frame and the leadingedge of the portrait will enable the tuned amplifier to provide onevalidating signal, and the portion of the background between thetrailing edge of the portrait and the trailing edge of the portraitframe will enable that amplifier to provide a second validating signal.Those two validating signals will then be used to cause acceptance ofthe inserted bill. By requiring two separate and distinct validatingsignals from each inserted bill, the present invention prevents theacceptance of spurious bills which might provide one validating signal,but could not provide two separate and distinct validating signals.Also, by obtaining one validating signal from the righthand half of theinserted bill and by obtaining the other validating signal from theleft-hand half of that bill, the present invention avoids the acceptanceof authentic bills that have been cut or split along their transverselyextending center lines. It is, therefore, an object of the presentinvention to obtain one validating signal from the portion of thebackground intermediate the leading edge of the portrait frame and theleading edge of the portrait of a bill and to obtain a second validatingsignal from the portion of the background intermediate the trailing edgeof the portrait and the trailing edge of the portrait frame of thatbill.

Many persons fold their paper currency along the longitudinallyextending center lines of that paper currency. Where paper currency isrepeatedly subjected to such folding, the longitudinally extendingcenter lines of that paper currency can become worn and frayed; and someof the ink at those center lines can be rubbed off and lost. The presentinvention avoids any reiection of authentic paper currency, that mightarise because of the loss of ink at the longitudinally extending centerlines of that paper currency, by mounting the magnetic head in registerwith portions of the paper currency that are offset laterally from thelongitudinally extending center lines of such paper currency. It is,therefore, an object of the present invention to mount the magnetic headin register with portions of the paper currency that are offsetlaterally from the longitudinally extending center lines of that papercurrency.

The portions of the backgrounds that are at opposite sides of theportraits on paper currency are not uniform in Width. Those variationsin width are due to the fact that the backgrounds are ovate, to the factthat the portraits are not full face, and to the fact that artisticconsiderations made width variations desirable. Those width variationskeep the total number of vertical or horizontal grid lines in theoppositely disposed portions of the backgrounds for the portraits ofbills from being uniform; and, hence, those width variations make itimpossible to obtain accurate and precise validating signals from thoseoppositely disposed portions of the backgrounds for the portraits merelyby adding up the total number of vertical or horizontal grid lines inthose oppositely disposed portions. This would be the case even if themagnetic head were in register with the longitudinally extending or thetransversely extending center line of the inserted bill; but it is evenmore the case where the magnetic head is set in register with portionsof the inserted bill that are laterally offset from the longitudinallyextending or the transversely extending center line of the bill andwhere the bill must be tested with its portrait either upright orinverted.

The preferred embodiments of the present invention make it possible tomount the magnetic head in register with portions of the inserted billthat are laterally offset from the longitudinally extending center lineof that bill, and make it possible to obtain two accurate and precisevalidating signals from the oppositely disposed portions of thebackground for the portrait of that bill whether that bill is insertedwith its portrait upright or inverted; and they do so by responding tothe phase, duration and repetition rate, rather than to the totalnumber, of the voltage variations due to the vertical grid lines in theoppositely disposed portions of the background for the portrait. such anarrangement is desirable because it keeps errors in the registry of theprinted area of the bill with the perimeter of the bill, due to errorsin the printing or cutting of the bill, from interfering with thegeneration of the required validating signals. Further, such anarrangement is desirable because it enables the required validatingsignals to be generated by authentic bills that are not held preciselyparallel to the path of movement of those bills, but, instead, areslightly skewed. It is, therefore, an object of the present invention totest for the phase, duration and repetition rate, rather than for thetotal number of the voltage variations due to the grid lines in theoppositely disposed portions of the backgrounds for the portraits ofpaper currency.

The voltage variations generated by the vertical or horizontal gridlines in the oppositely disposed portions of the backgrounds for theportrait of a bill can be fed into a tuned amplifier that will amplifythem and then use them to trigger a threshold-type control element toprovide validating signals. The tuned amplifier will be set to respondto a number of voltage variations that is slightly less than the minimumnumber of grid lines that will pass by the magnetic head as the narrowerof the oppositely disposed portions of the background for the portraitpasses by that magnetic head. Consequently, each of the oppositelydisposed portions of the background for the portrait will be able togenerate a validating signal, The use of a threshoid-type controlelement is desirable because once such a control element has beentriggered, it cannot restore itself as long as it continues to receiveamplified voltage variations. However, the nonreceipt of amplifiedvoltage variations, when the portrait'passes by the magnetic head, willallow the control element to restore itself. This means that if eitherof the backgrounds for the portrait has more grid lines than are neededto trigger the threshold-type control element, the additional grid linesWill not be able to cause that control element to provide a secondvalidating signal. Consequently, the present invention is able to obtainone, and only one, validating signal from each of the oppositelydisposed portions of the background for the portrait on an insertedbill. It is, therefore, an object of the present invention to feed thevoltage Variations, `obtained by the passage of an inserted bill, into atuned amplifier that will trigger a threshold-type control element toprovide one, and only one, validating signal from each of the oppositelydisposed portions of the background for the portrait on an insertedbill.

The preferred form of tuned amplifier provided by the present inventionincludes `a resonant circuit; and that amplifier amplifies the voltagevariations obtained from the magnetic head, responds to those amplifiedVoltage variations to provide quantums of energy, limits the maximumquantitative value of each quantum of energy, and then introduces thosequantums of energy into the said resonant circuit without appreciablyloading that resonant circuit. If the phase and repetition rate of thosequantums of energy substantially coincide with those of thecharacteristic wave form of said resonant circuit, and if the durationof those quantums of energy are such that the energy in each of thosequantums of energy is slightly greater than the losses of said resonantcircuit at some predetermined current value of said resonant circuit,and if enough of those quantums of energy are introduced within apredetermined period of time, the Value of the voltage across apredetermined part of said resonant circuit will gradually increase to apoint at which a threshold-type control element will become actuated.The limiting of the maximum quantitative value of each quantum of energycoacts with the requirement that the repetition rate and the phase ofthose quantums of energy substantially coincide with those of thecharacteristic wave form of said resonant circuit and with the furtherrequirement that the durations of those quantums of energy be such thatthe energy in each of those quantums of energy slightly exceed thelosses of said resonant circuit at some predetermined current value ofsaid resonant circuit, to enable said resonant circuit to interact withthe control element to pass a certain band of frequencies and to providevirtually infinite rejection of all other frequencies. This is verydesirable because it enables the currency detector provided by thepresent invention to reject spurious paper currency that is printed withmagnetic ink, but that does not provide voltage variations which havethe requisite phase, duration and repetition rate. It is, therefore, anobject of the present invention to provide a tuned amplifier that has aresonant circuit and that amplifies voltage variations, responds tothose amplified voltage variations to provide quantums of energy, limitsthe maximum quantitative value of each quantum of energy, and thenintroduces those quantums of energy into said resonant circuit, withoutappreciably loading that resonant circuit, to enable said resonantcircuit to operate a control element.

The low signal-to-noise levels of the voltage variations, generated whenthe inserted bill is moved past the air gap of the magnetic head, makeit necessary to base the identification of authentic paper currency onthe checking of a large number of grid lines. If the identification ofauthentic paper currency were to .be based upon the checking of justthree, four or five grid lines, three, four or five voltage variationsdue to noise could cause the acceptance of spurious paper currency. Anysuch acceptance of spurious paper currency would be objectionable, andit is avoided in the present invention by basing the identification `ofauthentic paper currency on the checking of a large number of gridlines. Thus, the present invention bases the identification of authenticpaper currency upon the checking of a minimum of twelve grid lines; sixof thoseV grid lines being intermediate the leading edge of thebackground frame and the leading edge of the portrait, and the other sixgrid lines being intermediate the trailing edge of the portrait and thetrailing edge of the background frame. It is, therefore, an object ofthe present invention to provide a currency detector that bases theidentification of authentic paper currency upon the checking of aminimum of twelve grid lines in the portrait backgrounds of insertedbills.

To keep the voltage variations generated .by one, two, three, four orfive grid lines from effecting the actuation of the control element, thepresent invention limits the maximum amplitude of all voltage variationsgenerated as the inserted bill passes the air gap of the magnetic head.As a result7 the resonant circuit cannot experience a rapid rise ofvoltage that would trigger the control element. Instead, the resonantcircuit must experience a controlled cumulative voltage growth as thesix or more Voltage variations from the six or more grid lines are in#troduced into the resonant circuit. In this way, full checking of six ormore grid lines is attained and definite identification of authenticpaper currency results. It is, therefore, an object of the presentinvention to provide a tuned amplifier that limits the maximum amplitudeof the voltage variations being translated thereby and that introducesthose limited voltage variations into a resonant circuit to effect acontrolled cumulative voltage in that resonant circuit.

It is important and desirable to be able to pass acertain band offrequencies and to reject all other frequencies.- It is even moreimportant to be able to pass a certain band of frequencies and toprovide virtually infinite re-` jection of all other frequencies. Wherethis is done, more of the frequency spectrum can be utilized effectivelybecause less of that frequency spectrum is needed to space apart thevarious bands of frequencies. The present in# vention makes it possibleto pass a certain band of -frequencies and to provide virtually infiniterejection of all other frequencies; and it is, therefore, an object ofthe present invention to pass a certain band of frequencies and toprovide virtually infinite rejection of all other frequencres.

The present invention is enabled to pass a certain band of frequenciesand to provide virtually infinite rejection of all other frequencies byproviding a resonant circuit, by providing a control element that has ahigh threshold value, and by introducing energy into said resonantcircuit, which has a maximum quantitative value that does not exceed apredetermined value, which has a quantitative value that is slightlygreater than the losses of said resonant circuit at some predeterminedcurrent value of said resonant circuit, which has a repetition rate andphase substantially coincident with those of the characteristic Waveform of said resonant circuit, and which is supplied in sufhcientquantity within a predetermined period of time to enable the voltageacross a predetermined part of said resonant circuit to rise to a pointWhere said control element will operate. That energy can be in the formof a generated wave form, a modulation, or voltage variations. Wherethat energy is initially formed in such a way that its quantitativevalue is within the required limits, neither limiting nor amplificationof that energy will be required; but where that energy is not initiallyformed in such a way that its quantitative value is within the saidlimits, limiting or amplification will be provided as required. In eachcase, the said resonant circuit will, if the energy has the requiredquantitative value and has the required repetition rate and phase, andif sufficient quantities of that energy are introduced within apredetermined period of time, experience a suficient increase in thevoltage across a predetermined part thereof to operate the controlelement. It is therefore, an object of the present invention to providea resonant circuit, to provide a control element that has a highthreshold value, and to introduce energy, into said resonant circuit,which has a maximum quantitative value that does not exceed apredetermined value which has a quantitative Value that is slightlygreater than the losses of said resonant circuit at a predeterminedcurrent value of said resonant circuit, which has a repetition rate andphase substantially coincident with those of said resonant circuit, andwhich is supplied in sufliicent quantity within a predetermined periodof time to enable the voltage across a predetermined part of saidresonant circuit to rise to a point where said control element willoperate.

The grids in the portrait backgrounds of the paper currency of theUnited States of America vary slightly with the denomination of thatpaper currency. By properly adjusting the tuned amplier of the presentin- Vention, it is possible to differentiate between authentic onedollar bills and authentic bills of the United States of America havingdifferent denominations. A-s a result, the currency detector of thepresent invention cannot only distinguish between spurious papercurrency and authentic paper currency, but it can also dierentiatebetween authentic pa er currency having different denominations. It is,therefore, an object of the present invention to provide a currencydetector that can differentiate between authentic paper currency havingdilferent denominations.

The authentic paper currency of the United States of America usually hasa green ink face and a black ink face; and it is the ink in the blackink face that is magnetic. The magnetic properties of the ink in theblack ink faces of paper currency of the United States of America are solimited that those faces must intimately abut the air gap of themagnetic head. It is usually possible, by means of suitable operatinginstructions, to cause the persons inserting bills in the currencydetector of the present invention to place those bills with the blackink faces up; and those black ink faces will then be moved into intimateengagement with the air gap of a magnetic head. Those black ink faceswill, irrespective of whether the portraits are upright or inverted,coact with the air gap of the magnetic head to provide the requiredvoltage variations. If the patrons in a particular area do not insertthe bills with the black ink face up, some of the embodiments of thecurrency detector provided by the present invention will still be ableto identify and accept those bills. In those embodiments of the currencydetector, one magnetic head is mounted to confront and engage one fadeof the inserted bills, and a second magnetic head is mounted to confrontand engage the other face of those bills. Consequently, the black inkface of an inserted bill will necessarily engage one or the other of themagnetic heads and thus be able to provide the requisite voltagevariations in the coil or coils of that particular magnetic head.

A bill which is to be tested by the currency detector provided by thepresent invention must be moved past an adjacent magnetic head at apredetermined rate of speed. That predetermined rate of speed must behigh enough to provide a usable signal-to-noise ratio. Further, the billmust be raised to that predetermined rate of speed very quickly, becausethat bill must be moving at a predetermined rate of speed when theleading edge of the portrait frame approaches that magnetic head; andthe distance between the leading edge of a bill and the leading edge ofthe portrait frame is necessarily less than one-half of the overalllength of the bill. The need of quickly raising the inserted bill to ahigh, predetermined rate of speed creates a problem, because thecurrency detector must use a small motor if that detectorl is to besmall and compact. The need of holding the the bill in intimateengagement with one or two magnetic heads during the testing of thatbill adds a further complication because that intimate engagementcreates appreciable frictional drag; and such drag would tend to keepthe bill from quickly reaching its high, predetermined rate of speed.The present invention makes it possible to use a small motor and to holdthe bill in intimate engagement with one or two magnetic heads duringthe testing of that bill, and yet quickly raises that bill to a high,predetermined rate of speed, by not urging the magnetic head or headsinto intimate engagement with that bill until after that bill has beenraised to its predetermined rate of speed. Once the motor has raised thebill to its high, predetermined rate of speed, that motor can continueto move that bill at that rate of speed despite the frictional dragcreated by the intimate engagement of one or two magnetic heads withthat bill. It is, therefore, an object of the present invention toprovide a currency detector `that does not urge the magnetic head orheads into intimate engagement with an inserted bill until that ball hasbeen raised t-o a high, predetermined rate of speed.

To assure the requisite intimate engagement between the black ink taceof an inserted bill and the magnetic head that is to engage that blackink face, a pressure member must be mounted in register with thatmagnetic head. Where the currency detector is equipped with two magneticheads, two pressure members will be required; and one of those pressuremembers will press against one face of the bill to urge the oppositeface of that bill against one of the magnetic heads, while the otherpressure member will press against the said opposite face of the bill tourge the said one face of that bill against the other magnetic head.Each magnetic head and its pressure member are in such intimateproximity in the positions they occupy when the bill is being testedthat they would prevent the ready introduction between them of theleading edge of an inserted bill if they always remained in thosepositions. Yet, such ready introduction of the leading edge of aninserted bill is vital to the successful operation of a currencydetector, because anything less than ready introduction of that leadingedge could cause crumpling, bending or rolling of the inserted bill; anda crumpled, bent, or rolled bill cannot be moved adequately, much lesstested adequately. Even fresh paper currency has only limited resistanceto crumpling, bending or rolling, and will worn paper cur-rency haslittle or no resistance to crumpling, bending or rolling. The preferredembodiments of the present invention assure ready introduction of theleading edge of an inserted bill between each magnetic head and itspressure member by spacing that magnetic head and pressure member apartuntil after the leading edge of that bill has passed between them; andthose embodiments assure subsequent intimate engagement between theinserted bill and that magnetic head by subsequently causing thatmagnetic head and its pressure member to tightly clamp that bill betweenthem. It is, therefore, an object of the present invention to hold themagnetic head and its pressure member apart until after the leading edgeof an inserted bill has passed between them, and then subsequently tocause that magnetic head and its pressure member to tightly clamp thatbill between them.

The inserted bill must be pressed against the air gap of the magnetichead with considerable force to keep wrinkles in the bill from causingsome of the grid lines in the portrait background to bow outwardly andaway from that air gap. The present invention makes certain that thegrid lines of inserted bills cannot bow outwardly and away from the airgap of the magnetic head, but instead, must intimately engage that airgap, by providing a pressure member that is in register with that airgap and that bends that bill into engagement with a substantial area ofthe face of that magnetic head. The resulting surface-to-surfaceengagement will be positive and certain whereas mere line contact mightnot. It is, therefore, an object of the present invention to provide apressure 9 member that is in register with the air gap of the magnetichead and that smooths Vout Wrinkles in the inserted bills and thatpresses each grid line in the portrait backgrounds of those bills intointimate engagement with the air gap of that magnetic head.

Where an inserted bill is tested and does not provide the voltagevariations which an authentic bill should provide, that inserted billmust be returned to the person who inserted it. In the preferredembodiments of the present invention, such a bill is moved back to theopening through which it was inserted. This means that unaccepted billswill retrace the movement they experienced during their testing. Itwould be impractical to try to make an unaccepted bill retrace itsmovement if the -inagnetic head and its pressure member continued toremain in the positions they assumed during the testing of that bill.Furthermore, it would be undesirable to have an unaccepted bill pass inintimate engagement with the magnetic head during its return movement;because that bill might be able to generate a validating signal duringthat return movement which could coact with a validating signalgenerated during the forward movement of that bill to provide an acceptsignal. The present invention assures full and free return movement ofunaccepted bills, and also keeps unaccepted bills from generatingvalidating signals during their return movement, by holding the magnetichead and its pressure member apart during the return movement ofunaccepted bills.

A bill that is to be tested must be readily gripped by the currencydetector, must be held tightly by that detector until it has beentested, must be promptly moved to the cash box if it is found to be anauthentic bill, and must be returned to the person who inserted it if itis found to be unacceptable. Further, the gripping of the bill must beaccomplished in such a way that the bill experiences no damage. Thepresent invention makes it possible for the currency detector of thepresent invention to meet all of these conditions; and it does so byequipping that currency detector with bill-engaging surfaces that arenormally spaced apart and that come together after the cycle of thecurrency detector has been initiated. Those bill-engaging surfacespositively hold a bill as they transport that bill past the magnetichead, and they move that bill past that head at a predetermined rate ofspeed. If that bill'is accepted, those surfaces will permit that bill tobe moved toward the cash box; but if that bill is not accepted, thosesurfaces will return that bill to its initial position. As thosesurfaces return the unaccepted bill to its initial position, thosesurfaces Will move out of engagement with that bill and thereby enablethe person who inserted that bill to retrieve it.

In some embodiments of the present invention, the bill' engagingsurfaces are a movable support and eccentrically mounted, gripping jawsthat are biased into engagement with that movable support. Thosegripping jaws are normally spaced away from that movable support, butthey move toward that movable support to grip an inserted bill as soonas that movable support starts to move. The eccentric mounting of thosegripping jaws enables those jaws to respond to eiorts to withdraw thebill to move into even tighter gripping engagement with the bill. Thosejaws'are moved away from the movable support after the bill has beentested, thereby facilitating movement of that bill to the cash box ifthat bill has been found to be authenti-c. `Those gripping jaws againmove toward the movable support when that movable support starts itsreturn movement; and, therefore, if an inserted bill has been found tobe unacceptable, those jaws will grip it and return it to the person whoinserted it. It is, therefore, an object of the present invention toprovide a movable support and eccentrically mounted gripping jaws thatare held out of engagement with that movable support when the currencydetector israt rest and when Ythe bill has been tested, and that areimmediately adjacent 10 those surfaces during the forward and returnmovement of thatl movable support.

Once the currency detector has determined that an inserted bill isauthentic, an acceptance mechanism becomes operable and quicklytransfers that bill to the cash box. In some embodiments of the presentinvention, the acceptance mechanism causesthe accepted bills to passadjacent an eccentrically mounted element that freely and readilypermits movement of those bills toward the cash box, but fully andcompletely prevents movement of those bills in the opposite direction.That eccentrically mounted element thus makes it virtually impossiblefor a person to attach a string, a thread, a wire, a strip of paper, astrip of cloth, or other tail to an inserted bill and withdraw that billfrom the currency detector after that bill has generated validatingsignals. It is, therefore, an object of the present invention to providean acceptance mechanism that transfers authentic bills to the cash boxVand moves saidbills past an eccentrically mounted element that preventsreturn movement of said bills.

The currency detector provided by the present invention is-providedwwithan over-level control which will present the acceptance of insertedbills that have ink with excessive magnetic properties. This over-levelcontrol will reject any spurious bills that have unduly strong, magneticink,and the tuned` amplifier of the currency detector will reject anyspurious bills that have insuiciently strong magnetic ink. As a result,a counterfeiter would not only have to match the spacing and widths ofthe grid lines in the backgrounds of the portraits of bills, but hewouldalso have to match the magnetic properties of the ink used. It is,therefore, an object of the present invention -touprovide an over-levelcontrol for a currency detector. f.,

Other and further objects and advantages of the present invention shouldbecome apparent from an examination of the drawings and accompanyingdescription.

' In the drawings and accompanying description, several embodiments ofthe present invention are shown and described, but it is tobe understoodthat the drawing and accompanying description are for the purpose ofillustration only and do not limit the invention and that the inventionwill be defined by the appended claims.

In the drawing:

FIGURE 1 is a partially-sectioned, partially-broken side elevationalview of one embodiment of currency detector that is made in accordancewith the principles and teachings of the present invention;

FIGURE 2 is a diagrammatic suggestion of the Vportrait and background ofa one dollar bill of the United States of America; j

FIGURE/3 is a front elevational view of a portion of the front plate ofthe currency detector of FIGURE 1;

FIGURE 4 is a partially broken plan view of the currency detector ofFIGURE 1;

. FIGURE 5 is a sectional view through the currency detector of FIGUREl, and it is taken along the broken plane indicated by the line 5-5 inFIGURE l; u Y

FIGURE 6 is a sectional view through the currency detector of FIGURE 1,and it is taken along the plane indicated by the line 6-6 in FIGURE 4;

FIGURE 7 is another sectional View through the currency detector ofFIGURE 1, and it is taken along the broken plane indicated by the line7-7 in FIGURE 1;

FIGURE 8 is a partially sectioned plan view showing the two magneticheads of the currency detector of FIGURE 1;

FIGURE 9 is a sectional view through the currency detector of FIGURE 1,and it is taken along the plane indicated by the line 9 9 in FIGURE 7;

FIGURE l0 is the wiring diagram of the currency de tector of FIGURE land of a typical vending machine with which that currency detector canbe used;

FIGURE 11 isla side elevational view of another embodiment of currencydetector that is made in accordance 1 1 with the principles andteachings of the present invention, but that currency detector has beenrotated one hundred and eighty degrees around a vertical axis from theposition occupied by the currency detector in FIG- URE 1;

FIGURE 12 is a partially broken plan view of a portion of the right-handend of the currency detector of FIGURE 11, but it shows that end as ithas been rotated one hundred and eighty degrees about a vertical axisfrom the position occupied by it in FIGURE 11;

FIGURE 13 is a partially broken sectional View through the portion ofthe currency detector shown in FIGURE l2, and it is'taken along theplane indicated by the line 13-13 in FIGURE 12;

FIGURE 14 is the wiring diagram of the currency detector of FIGURE l1and of a typical vending machine with which that currency detector canbe used;

FIGURE 15 is a partially sectioned, partially broken side view ofanother embodiment of currency detector that is made in accordance withthe principles and teachings of the present invention;

FIGURE 16 is a sectional view on an enlarged scale, through the currencydetector of FIGURE 15, and it is taken along the broken plane indicatedby the line 16-16 in FIGURE l;

FIGURE 17 is a sectional view on said enlarged scale, through theportion of the currency detector shown in FIGURE 16, and it is takenalong the plane indicated by the line 17-17 in FIGURE 16;

FIGURE 18 is a partially sectioned, partially broken plan view of thecurrency detector of FIGURE FIGURE 19 is a sectional view on theenlarged scale of FIGURE 16, through the currency detector of FIG- UREl5, and it is taken along the plane indicated by the line 19-19 ofFIGURE 15;

FIGURE 20 is a broken away side view on a slightly enlarged scale ofpart of the currency detector of FIG- URE 15, and it shows the carrierfor the bills in moved position;

FIGURE 2l is a sectional view on a still larger scale, through thecurrency detector of FIGURE 15, and it is taken along the planeindicated by the line 21-21 in FIGURE 15;

FIGURE 22 is a sectional view on the scale of FIG- URE 2l, through thebill carrier of FIGURE 15, and it is taken along the plane indicated bythe line 22-22 in FIGURE 18;

FIGURE 23 is a sectional view on the scale of FIG- URE 16, through thecurrency detector of FIGURE 15, and it is taken along the planeindicated by the line 23-23 in FIGURE 15;

FIGURE 24 is a perspective view on an enlarged scale, showing theposition which four magnetic heads will occupy if four, rather than justtwo, magnetic heads are used in the currency detectors of FIGURES 1 and11;

FIGURE 25 is a schematic view of a magnetic head which has a permanentmagnet formed as a part of the flux path thereof;

FIGURE 26 is a schematic view of a magnetic head which has a permanentmagnet adjacent the air gap thereof;

FIGURE 27 is a rear elevational view of one form of magnetic 1lead thatis usable with the currency detectors of the present invention;

FIGURE 28 is a bottom view showing the air gap of the magnetic head ofFIGURE 27;

FIGURE 29 is the wiring diagram of the currency detector of FIGURE l5and of a typical vending machine with which that currency detector canbe used;

FIGURE 30 is the wiring diagram of a preferred form of tuned amplifierand control element usable with any of the currency detectors of FIGURES1-29; and

FIGURE 3l shows the circuit of a multi-channel tuned amplier and of thecontrol elements therefor.

Components yof embodiment of currency detectOr shown by FIGURES 1-10Referring to FIGURES 1-10, the numeral 50 denotes the front plate of anembodiment of currency detector that is provided by the presentinvention. That plate has an opening 52 through which has the form of auinverted T. A finger-receiving recess is provided on that front plate inregister with the opening 52, and that recess extends rearwardly fromtheupper portion of that opening. That recess has side wall 54, has asharply inclined upper rear wall portion 56, and has a less sharplyinclined rear portion 58. The bottom of that finger-receiving recess isopen. A generally L-shaped stop 60, particularly by FIG- URES 4 and 6,is secured to the rear face of the front plate 56 at a point below andto the left of the opening 52. A substantially identical stop 62 issecured to the rear face of that front plate at a point below and to theright of the opening 52. Fasteners 64, such as rivets, bolts or thelike, extend through the front plate 50 and permanently secure the stops60 and 62 in position at the rear face of that plate. As indicatedparticularly by FIG- URE l and by FIGURE 6, the stops 6@ and 62 extendupwardly and rearwardly from the rear face of the front plate 50.

The numeral 68 denotes the rear plate of the currency detector shown byFIGURES 1-10; and that rear plate is vertically directed and hasrearwardly extending flanges 7i) and 72 at the opposite sides thereof.The rear plate 68 has a large, centrally located, generally rectangularopening 74 through it. A pin 76 is secured to and projects outwardlyfrom the rearwardly extending flange '72 of the rear plate 68, as shownby FIGURE l. A threaded opening, not shown, is provided in the flange 72above the level of the pin 76, and a vertically elongated opening 78 isprovided in that flange at a point to the right of, and slightly belowthe level of, the pin 76, as shown by FIGURE l. A circular opening 80 isprovided in the lange 72 below the level of the opening 78.

vAn L-shaped bracket 82 is secured, by welding or otherwise, to the rearface of the rear plate 68 adjacent the bottom edge of the opening 74, asshown by FIGURE, 6. That L-shaped bracket is horizontally directed, butit is shorter than the width of the opening 74. A second L-shapedbracket 84 is secured to the rear face of the rear plate 68, as shown byFIGURE 4. That bracket is spaced inwardly from the liange 7G, and it isvertically directed.. That bracket is located above the level of theopening 74- in rear plate 63; and fasteners 86, such as rivets, screwsor the like, secure that L-shaped bracket to the rear plate 68.

A bar 88 with a rounded face 90 is secured to, and projects forwardlyfrom, the front face of the rear plate 68, as shown by FIG. 1. That bar88 is disposed closely adjacent one of the sides of the rear plate 68,as shown by FIG. 4. A bar 92 which is identical to the bar 88 is alsosecured to, and projects forwardly from, the front face of the rearplate 68. That bar is closely adjacent the other side of the rear plate68, and it is on the same level as the bar S8. Fasteners 94, such asrivets, riveted-over extensions of the bars 88 and 92, or screws, areprovided at the rear face of the rear plate 68 to permanently hold thebars 88 and 92 in assembled relation with that rear plate.

The numeral 98 denotes the elongated top plate of the currency detectorshown by FIGS. 1-10. That top plate is provided with a downwardlyextending flange 106 at one of the elongated sides thereof; and it isprovided with a second, and substantially identical, downwardlyextending frange 162 at the opposite side thereof. Each of the sideflanges (see FIG. 1) has a shallow, horizontally directed portionextending rearwardly from the front thereof, has a downwardly andrearwardly inclined portion contiguous with the rear of said shallow,horizontally directed portion, has a deep, horizontally directed portioncontiguous with and extending rearwardly from the bottom of thedownwardly and rearwardly inclined portion, has an arcuate downwardlyextending protuberance adjacent the rear edge of said deep horizontallydirected portion, has a vertically directed portion extending unwardlyfrom the rear edge of said protuberance, and has a third horizontallydirected portion contiguous with and extending rearwardly from the topof said vertically directed portion. The various portions of the flanges100 and 102 are squarely in register with each other. A sha1- low flange104 extends downwardly from the front edge f the top plate 98, and thatflange is as deep as the shallow, horizontally directed portionsadjacent the front edges of the flanges 100 and 102. A shallow flange106 extends downwardly from the rear edge of the top plate 98, and thatflange is as deep as the rearmost horizontally directed portions of theflanges 100 and 102. Fasteners 108, such as rivets, bolts or the like,extend through alined openings in the rear flange 106 and in the rearplate 68 to permanently secure the top plate 98 to the rear plate 68.Fasteners 110, such as rivets, bolts or the like, extend through aline-dopenings in the front flange 104 and in the front plate 50 topermanently secure the top plate 98 to the front plate 50.

A U-shaped bracket 112 is provided with laterally directed flanges atthe upper ends of the arms thereof, and those flanges abut the underface of the top plate 9S at a point close to the front end of that topplate. Fasteners 114, such'v as rivets, bolts or the like, extendthrough alined openings in the top plate 98 and in the flanges at theupper ends of the arms of the U-shaped bracket 112 to permanently securethat bracket to that top plate. The numeral 116 denotes a solenoid whichis fixedly held by the bracket 112 and which has a plunger 4118 thatextends downwardly through a small opening in the bottoni of thatbracket. A helical compression spring 120 has the upper end thereofabutting the lower end of the bracket 112 and has the lower end thereofabutting a washerwhich is held in position on the plunger 118 by Ia pin.The spring 120 biases the plunger 118 for movement downwardly relativeto the bracket 112; but the solenoid 116 is able, whenever it isenergized, to overcome the force of the spring 120 and to raise theplunger 118 to the retracted position shown by FIG. 6. However, when thesolenoid 116 is deenergized, as it is when the embodiment of currencydetector shown by FIGS. 1-10 is at rest, the spring 120 will hold theplunger 118 in the lower position shown by FIG. l.

The numeral 122 denotes a vertically directed pin which has a threadedupper end extending upwardly through an opening in top plate 98 at apoint rearward of the U-shaped bracket 112. A nut 124 is threaded ontothe upper end of the pin 122 before that upper end is passed through theopening in the top plate 98; and a second nut is subsequently threadedonto that upper end of the pin 122. The nuts 124 fixedly secure the pin122 in position relative to the top plate 98.

The numeral 126 denotes a solenoid which has laterallyextending flangesat the top thereof. Those flanges abut the under side of the top plate98 adjacent the rear of that top plate; and fasteners 130, such asrivets, bolts or the like, extend through alined openings in thoseflanges and Vin the top plate 98 to permanently secure that solenoid tothat top plate. The solenoid 126 has an armature 128 that extends to theleft from that solenoid. The solenoid 126 is larger and more powerfulthan the solenoid 116.

A pin 132 is secured to the flange 102 intermediate the pin 122 and theplunger 128 of the solenoid 125, as

shown by FIG. 6. That pin is disposed below the level of the top plate98, and it extends horizontally toward the flange 100. Y

The numeral 136 denotes the elongated bottom plate of the currencydetector shown by FIGS. l-l; and that bottom plate has shallow,upstanding flanges 1-38 and 140 at the sides thereof. A shallow flange-142 extends upwardly from the front of the bottom plate 136, and theupper edge of that flange is at the level of the upper edges of theflanges 138 and 140. A shallow flange 144 extends upwardly from the rearof the bottom plate 138, and the upper edge of that flange is at thelevel of the upper edges of the flanges 138 and 140. Fasteners 146, suchas rivets, bolts or the like, extend through alined openings in thefront flange 142 and in the front plate `50 to permanently secure thebottom plate 136 to the front plate 50. Fasteners 148 such as rivets,bolts or the like, extend through alined openings in the rear flange 14dand in the rear plate 68 to permanently secure the bottom plate,

136 to the rear plate 68.

A small opening 150 is provided in the Hang-'e140 adjacent the rear ofthat flange. A similar opening, not shown, is provided in the flange 138adjacent the rear of that flange; and the axes of those openings arealined.

A U-shaped bearing bracket 152, with spaced upstanding arms, is suitablysecured to the bottom plate 136 intermediate the side flanges 13S and140. That bearing bracket is immediately adjacent the rear flange 144;and alined openings are provided in the upstanding arms of that bearingbracket. j

The numeral 154 denotes a singlepole, single-throw switch that issecured to the outer face of the flange 140 on the bottom plate 136.That switch is secured to that flange by fasteners 156, such as screws,which extend through passages in the switch housing and which seat inthreaded openings in` the flange 140. The contacts of that switch arebiased'toward closed position, but the resilient actuator 158 of thatswitch can be moved downwardly to cause those contacts to open.

The numeral 160 denotes a stud which has a reduced diameter lower endthan extends downwardly through the opening in the bottom plate 136 andis; then riveted over to permanently secure that stud to that bottomplate. The upper end of the stud 160 isalso reduced indiameter, andtnatupper end serves as a pivo't.- The numeral 162 denotes a smallerdiameter studwhich 'has a reduced diameter lower end than extendsthroughan opening in the bottom plate 136 and is then riveted over. The upperend of the stud 162 also serves as .a pivot.

The numeral 164 denotes a motor which is encased in an iron or steelhousing; and that housing will confine the stray fields emanating fromthe motor. Elongated screws 165 extend upwardly through the housing ofthe motor 164 and through openings in the bottom plate 136. Nuts 167 arethreaded onto the upper ends of those screws, and they will co-act withthose screws to hold the motor 154 and its housing in assembled relationwith the bottom plate 136. The motor 154 is a synchronous motor and itwill move an inserted bill through the currency detector atapredeterminned speed.

The numeral 166 denotes a U-shaped bracket which is adjacent the rear ofthe bottom plate 136, and that bracket has inwardly extendingprojections at the free ends of the arms thereof. Those projections aredimensioned to extend through the opening 150 in the flange 140 andthrough the c-or-responding opening, not shown, in the flange 138.Washers 168 are telescoped over the inwardly extending projections onthe arms of the bracket 166 before those projections are passed throughthe the openings in the flanges 138 and 140, and those Washersfacilitate ready rotation of that bracket relative to those flanges. Aguide pulley 170, for bead chain, is rotatably mounted on, and carriedby, the closed end of the bracket 166. A helical extension spring 172has one end thereof hooked around the closed end of the bracket 166, andhas the other end thereof passed through an opening, not shown, in theL-shaped bracket 82 secured to the rear face of rear plate 68. Thatspring urges the pulley downwardly and lto the right in FlG. 6.

The numeral 176 denotes a platform which extends forwardly from thefront-plate 50. That platform has shallow upstanding flanges 178 at thesides thereof, and those flanges are spaced apart by a distance which isjust slightly larger than 'the distance between the elongated edges ofcurrency of the United States of America. A projection 180 extendsdownwardly from the bottom face of the platform 176, as shown by FIG. l;and that projection is set forwardly a short distance from the rear ofthe platform 176. Consequently, when the rear face of the projection 188is set in abutting relation with the front face of front plate 50, therear portion of the platform 176 extends through the bottom of theT-shaped opening 52. Fasteners 182, such as rivets, bolts or the like,secure the projection 188 to the front pla-te 50 and thereby fixedlysecure the platform 176 to that front plate. A wide but shallow recess184 is provided in the top face of the rear portion of the platform 176.

A bed plate 188 is provided for the currency detector of FIGS. 1-10, andthe front end of that bed plate rests in the wide but shallow recess 184of the platform 176. The thickness of the bed plate 188 is such thatwhen its front end rests in the recess 184, the top of that bed plateand the top of the platform 176 are in the same plane. Fasteners 193,such as rivets or the like, permanently secure the bed plate 188 to theplatform 176, as shown by FIG. 5. The bed plate 188 has downwardlyextending sides 192; and those sides have laterally extending flanges194 at the lower edges thereof. The bed plate 188 is made of sturdymetal, and it is made heavy enough that it will not warp r distort.

An opening 196 is provided in the bed plate 188 adjacent the frontthereof, and an opening 198 is provided in that bed plate adjacent therear thereof, all as shown by FIG. 6. An opening 208 is provided in eachof the downwardly extending sides 182 of bed plate 188, and thoseopenings have their axes alined, as shown by FIG. 5; but one of theopenings 280 is larger than `the other. Openings 282 are also providedin the downwardly extending sides 192 of bed plate 188; and one of thoseopenings is larger than the other, as shown by FIG. 5. A shallow,downwardly extending flange 284 is provided at the rear edge of bedplate 188, and that flange has a vertical slot intermediate its sideedges. Fasteners, not shown, permanently secure the flange 204 to therear plate'68, to hold that bed plate fixed -relative to that rearplate.

The front plate 50, 4the rear plate 68, the top plate 98, the bottomplate 136, and the bed plate 188 coact to provide a strong, rigid andunyielding frame work for the currency detector shown by FIGS. l-lO.That trainework is stiff enough to make it possible lto mount the4currency detector shown by FIGS. 1-10 in the housing of a vendingmachine by securing the top plate, the 'bottom plate, the front plate,or the rear plate thereof to one of the structural members of thatvending machine. The front plate 50 will be disposed adjacent an openingin the housing of `the vending machine so that the platform 176 willproject outwardly from one face of that housing to give the patronaccess to the finger-receiving recess of front plate 50.

The numeral 208 denotes a confining plate that is disposed a shortdistance above the bed plate 188. That confining plate has a front ange210 which is inclined forlwardly and upwardly to abut the portion 58 ofthe rear wall of the finger-receiving recess. Fasteners 212, such asrivets, bolts or the like, extend through alined openings in the wallportion 58 and in the flange 210 -to permanently secure the confiningplate 288 to the `front plate 58. A flange 214 projects upwardly andrearwardly from the rear of the confining plate 208, and it is securedto the rear plate 68 by fasteners 216, such as rivets, bolts or thelike. An opening 218 is provided in the confining plate 208 adjacent thefront thereof, as shown by FIGS. 4 and 6, and that opening accommodatesthe lower end of plunger 118. That opening permits the bottom of `thatplunger to rest upon the bed plate 188, whenever 16 solenoid 116 isde-energized, and thereby limit the extent to which a bill can beintroduced into the currency detector. If desired, an opening or recesscould be provided in the bed plate 188, in register with the opening21S, to enable the lower end of the plunger 118 to extend below thelevel of the upper face of bed plate 188; but such an opening or recesshas not been found to be necessary.

An opening 228 is provided in the confining plate 208; and that openingis located a short distance rearwardly of the opening 21S, as shown byFIGS. 4 and 6. The opening 220 is generally rectangular in plan, but ithas a narrow extension that is closely adjacent the opening 218 as shownby FIG. 4. An opening 222 is provided in the confining plate 288adjacent the rear thereof, as shown by FIG. `6. The confining plate 288is spaced far enough above the bed plate 188 to permit a bill to beinserted between those plates, but that confining plate will helpconfine such a bill and will `help keep it from crumpling, bending, orrolling as it is moved relative to the bed plate 188.

The numeral 226 generally denotes a bill carrier that is supported byand is movable relative to the bed plate 188; and that carrier is shownby FIG. 7. That carrier includes a rigid and sturdy U-shaped frame 228.Bearing locks 238 are secured to the inner faces of the upstanding armsof that frame by fasteners 232, such as screws, bolts or the like. Thebottom faces of the bearing plates 238 are spaced above the closed endof the frame 228 distances which are slightly greater than thethicknesses of the outwardly extending flanges 194 on the downwardlydepending sides 192 of bed plate 188. Those bearing plates coact withthe closed end of the frame 228 to enable the bed plate 188 to guide anyand all movement of the carrier 226.

The numeral '234 denotes an elongated pin which is secured to theright-hand arm of the frame 228, and that pin rotatably supports aroller sleeve 236. A C-washer 238 seats in a groove adjacent the outerend of the pin 234 and thereby prevents accidental separation of thatroller sleeve from that pin.

Two short shafts 240 are rotatably mounted in open.- ings, not shown, inthe upper portions of the arms of the frame 228. The outer ends of thoseshafts support levers 242, and the hubs of those levers are xedlysecured t0 those shafts by pins 244. The pins 244 project radiallyoutwardly beyond the outer peripheries of the hubs of levers 242 to holdthe ends of helical extension springs 248. The inner ends of the shortshafts 240 have discs 246 secured to them, and those discs have ilatfaces adjacent the bottoms thereof, as shown by FIG. 9. Those discs arelocated above the bearing plates 230, and they can be rotated until theflat faces thereof are parallel to those bearing plates. Those discs canalso be rotated until the trailing edges of their tlat faces eitherengage or are immediately adjacent the upper surfaces of the bearingplates 230, as shown by dotted lines in FIG. 9. The flat faces, andthose portions of the peripheries of the discs 2de adjacent the trailingedges of those iat faces, are covered with a material, such as cork,rubber, elastomeric plastic or the like, which has a high coefficient offriction. Pins 250 extend outwardly from the arms of the frame 228 tosupport the other ends of the helical extension springs 248. Thosesprings bias the flat faces of the discs 246 toward the bearing plates238, but those springs can yield to permit those discs to be rotatedinto the raised position shown by solid lines in FIG. 9. When the discs246 are in that raised position they will permit ready insertion andready removal of bills into and from the 4currency detector. I wever,when those discs are in the dotted line position shown by FIG. 9, theywill engage the edges of a bill and force that bill into holdingengagement with the bearing plates 238; the upper faces of those bearingplates constituting bill-receiving surfaces. The discs 246 are mountedeccentrically on the short shafts 248; and any effort to withdraw abill, by moving it

1. APPARATUS FOR IDENTIFYING AUTHENTIC PAPER CURRENCY EVERY TRUE EXAMPLEOF WHICH HAS A FIRST MAGNETIC ELEMENT CONSISTING OF AN AREA ON THE FACEOF THE CURRENCY HAVING MAGNETIC MATERIAL ARRANGED TO PROVIDE VARIATIONSOF MAGNETIC PROPERTIES ON A PARTICULAR PREDETERMINED PATTERN ALONG ACERTAIN PATH ACROSS THE SAID AREAS, WHICH MAGNETIC PROPERTIES MAY BEWEAK, THE APPARATUS COMPRISING: A BASE, A MAGNETIC HEAD ON THE BASE,SAID MAGNETIC HEAD HAVING A SECOND MAGNETIC ELEMENT CONSISTING OF APIECE OF MAGNETIC MATERIAL AND AN ELECTRICAL CONDUCTOR ASSOCIATED WITHTHE PIECE OF MAGNETIC MATERIAL, IN WHICH VOLTAGE VARIATIONS MAY BEPRODUCED BY CHANGES IN MAGNETIC FLUX IN AND ADJACENT THE SECOND MAGNETICELEMENT; MEANS FOR SUPPORTING THE CURRENCY ON THE BASE; AT LEAST ONE OFTHE TWO MAGNETIC ELEMENTS BEING MAGNETIZED TO PRODUCE A MAGNETIC FIELDIN IT AND ADJACENT TO IT; MEANS FOR PRODUCING RELATIVE MOVEMENT OF THECURRENCY SUPPORTING MEANS AND THE MAGNETIC HEAD TO CAUSE SAID SECONDMAGNETIC ELEMENT TO MOVE AT A PREDETERMINED SPEED ALONG A PREDETERMINEDPATH ACROSS THE SAID MAGNETIC AREA OF THE CURRENCY, SAIDMOTION-PRODUCING MEANS INCLUDING MEANS TO DISPOSE THE MAGNETIC AREA OFTHE FIRST SAID MAGNETIC ELEMENT IN INITI-